The invention concerns in particular an automatic chemical analytical apparatus comprising                an automatic pipetting unit for aspirating a sample portion from a selected sample tube from an array of sample tubes located in a sample tube area, and for delivering said aspirated sample portion to a selected reaction tube from an array of reaction tubes located in a reaction tube area, each sample tube carrying on it an identification readable by a reader device,        a plurality of elongated sample racks, each of which has a length axis and is adapted to accommodate a plurality of sample tubes, each sample tube being filled with a sample, each sample rack carrying on it an identification readable by a reader device,        a rotatable sample rack carrier located in said sample tube area, said rotatable sample rack carrier being adapted to accommodate a plurality of said sample racks within a space delimited by a circumference, said sample racks being arranged along said circumference with the length axis of each of said sample racks substantially orthogonal to said circumference.        
An analytical apparatus of this kind is described in European Patent Specification No. EP 0325101 B1. This document contains no description of any means for automatically transporting sample racks from a rack supply unit to the rotatable sample rack carrier and for positioning the sample racks on that rack carrier or for automatically removing the sample racks from that carrier and transporting them back to the rack supply unit. Therefore, according to EP 0325101 B1, the latter transport and positioning and removing operations have to be done manually.
In order to improve the reliability of the operation of such an analytical apparatus and generally in order to improve the overall performance of such apparatus, it is desirable to avoid as much as possible any manual operations for the transport of the sample tubes.
The aim of the invention is therefore to provide an analyzer of the above mentioned kind wherein the transport of the sample tubes is completely automated.